1. Field of the Invention
The present invention relates to a digital video disk (hereinbelow, referred to as "DVD") player, and more particularly, to a method and apparatus of improving reliability of a data descrambling operation.
2. Description of the Related Art
With the arrival of the multimedia era, a continuing effort is being increased sharply and great progress has been made recently, to transmit various kinds of information more rapidly and accurately through a combination of digital communication technologies. A very large scale integrated (VLSI) circuit and a digital signal processing technique, image, audio and other data which had been produced and processed independently in the past can be processed and used in various forms without distinction of information source or medium. In such surroundings, needs are raised for international transmission standardization of digital data for the purpose of easy information transmission and sharing between different systems.
Consequently, standardization for JPEG (Joint Photographic Coding Experts Group) of ISO/ITU-TSS (International Organization for standardization/International Telecommunication Union-Telecommunication standardization Sector) as well as MPEG (Moving Pictures Experts Group) of ISO/IEC (International Electrotechnical Commission) has been accomplished.
As a result, a digital data compression technique could be developed considerably. Particularly, MPEG-2 can reproduce picture quality of a level received at home at an information transmission rate which is a little less than 10 Mbps presently. Further, the advent of AC-3 for audio compression technique, which enables multi-channel audio reproduction in an audio field, makes it possible to enjoy audio and multi sound of high quality at home. It is expected that a DVD which appeared under such a technical background would play many parts in the functions of a VTR, i.e., a conventional picture recording/reproducing apparatus and a CD-ROM together with a DVD-R will appear in the near future. The DVD as one type of digital moving pictures storing disk media is a widely used type of multimedia storing device having high picture quality and high tone quality.
FIG. 1 is a block diagram showing the inner construction of a conventional DVD player. Referring to FIG. 1, a digital video disk (hereinbelow, referred to as a "disk") 10 rotates at a predetermined speed by rotation of a disk motor 16. A pickup 12 projects a laser light beam on the disk 10 to readout data therefrom, receives the reflected light beam, and converts the reflected light beam into an analog RF (Radio Frequency) signal. A sled feed motor 14 performs the feeding of the pickup 12. A signal reproducing section 18 executes the reproducing operations of the data recorded on the disk 10, such as amplification of the RF signal output from the pickup 12, noise elimination thereof, conversion of the analog RF signal into a digital signal and sync detection. A servo controller 26 performs control of the disk rotation for an exact readout of the data recorded on the disk 10, a focusing of the pickup 12 and a tracking control. A system controller 24 controls overall operations for reproduction of the data recorded on the disk 10. A memory 22 which is used as a track buffer, and which is connected to a digital signal processor (DSP) 20, stores data processed therein. The digital signal processor 20 16-8-demodulates a signal input from the signal reproducing section 18, executes a phase control operation by PLL (Phase Locked Loop), a descrambling operation, an error detection operation, an error correction operation and the control operation of the memory 22.
FIG. 2 is a detailed block diagram showing the inner construction of the digital signal processor 20 shown in FIG. 1. Referring to FIG. 2, the digital signal processor 20 includes a 16-8 demodulator 60 which detects a sync of input data to 16-8 demodulate it, and then stores the demodulated data in the memory 22 under the control of a memory controller 70. An ID error correction section 64 receives ID data indicative of the position of the disk 10 from the memory 22 through an ID and data discriminator 62 and corrects an ID error to supply the corrected ID data to the system controller 24. Error corrected ID data are used for the system controller 24 to control a disk servo. A total data error correction section 66 reads again total data (ID+main data) stored in the memory 22 to correct an error of the total data, and then stores again the corrected results in the memory 22 under the control of the memory controller 70. The error corrected total data are descrambled in a descrambler 68. The descrambler 68 uses ID data during the descrambling of the total data. The descrambled total data are stored again in the memory 22, and if there is a request for the data from an audio/video decoding section 100, the descrambled total data are supplied to the audio/video decoding section 100 which includes a demultiplexer 32 and an audio/video decoding section 34.
Referring again to FIG. 1, a key input section 28, as a user interface, includes a plurality of keys for instructing the operations such as reproduction, stop, seek. A display unit 30 displays various kinds of display data associated with data reproduction under the control of the system controller 24. An MPEG-2 decoder 34 includes a video decoder 36, a sub-video decoder 38, a Video Blanking Information (hereinbelow, referred to as "VBI") decoder 40 and a High Light Information (hereinbelow, referred to as "HLI") decoder 42 and an audio decoder 44. The video decoder 36 decodes compressed video data and outputs the decoded data in a digital video form to a video mixer 46. The sub-video decoder 38 decodes sub-video information into still pictures and outputs the decoded information to the video mixer 46. The VBI decoder 40 and the HLI decoder 42 decode data of still picture form in such a manner as to conform with a special use and output the decoded data in a digital video form to the video mixer 46. The audio decoder 44 decodes audio data and outputs the decoded data in a digital audio form to an audio output section 50. The video mixer 46 mixes together the outputs of the video decoder 36, the sub-video decoder 38, the VBI decoder 40 and the HLI decoder 42 output in a digital video form, and converts the mixed outputs into a suitable form so that they can be displayed on one screen. A video output section 48 converts the video signals of a digital form into video signals of an analog form and outputs the converted video signals to a monitor (not shown). The audio output section 50 converts audio signals of a digital form into audio signals of an analog form and amplifies the converted audio signals to output the amplified audio signals to a speaker (not shown). A demultiplexer 32, as a data phaser, classifies a type of bit streams, i.e., a video signal, an audio signal and a sub-audio signal and supplies each of the classified signals to the corresponding decoders in the MPEG-2 decoder 34.
In the digital signal processor 20 of such a DVD player, firstly, separate error correction of only ID data improves an exactness of information necessary for detecting the present position on the disk. After that, if the desired position on the disk is detected using the error corrected ID data, desired data are read from the disk, and the read data are stored in the memory 22 until preset total data blocks (182 bites.times.208 bites) are input to the memory 22. If the total data blocks are stored in the memory 22, the total data error correction section 66 reads the total data stored in the memory 22 to correct errors of the total data. At this moment, the error correction of ID data and main data is carried out simultaneously. The error correction of ID data is performed twice because ID data are very important information indicative of an address of each sector on a disk. However, although the error correction of the total data are carried out exactly, for an actual case, an error may be caused in the ID data due to various factors. If an error is generated in the ID data, the descrambling of data corresponding to each sector on the disk is not executed well.